Brake device in tape recorder

ABSTRACT

A brake device in a tape recorder which includes a brake band entrained on a braked drum for movement in the direction of the braked drum, whereby one end portion of the brake band engages stop means in accordance with the direction of rotation of the braked drum to thereby provide a slack end portion of the brake band, while the other end portion of the brake band provides a tight portion to which is imparted a spring force having a predetermined characteristic.

United States Patent Yoshii [4 1 Mar. 28, 1972 [54] BRAKE DEVICE IN TAPERECORDER [72] Inventor: Tetsuji Yoshii, Neyagawa, Japan [73] Assignee:Matsushlta Electric Industrial Co., Ltd.,

Osaka, Japan 221 Filed: Mar.3l,197 0 [21] Appl.No.: 24,219

[30] Foreign Application Priority Data Oct. 7, 1969 Japan ..44/80056[52] US. Cl. ..l88/77 R, 188/171 [51] Int. Cl. ..Fl6d 49/00, B60t 13/04[58] Field of Search ..188/77 R, 166, 171

[56] References Cited UNITED STATES PATENTS 998,976 7/1911 Moody..188/171 2,641,338 6/1953 Findley ..188/171 X 3,092,345 6/1963 Claytonet a1 ..l88/77 X FOREIGN PATENTS OR APPLICATIONS 563,517 9/1923 France..188/77 592,187 4/1925 France ...188/77 184,585 6/1907 Germany 188/77966,666 8/1957 Germany 188/77 961,185 6/1964 Great Britain 188/166Primary Examiner-Duane A. Reger Attorney-Stevens, Davis, Miller & Mosher[5 7] ABSTRACT A brake device in a tape recorder which includes a brakeband entrained on a braked drum for movement in the direction of thebraked drum, whereby one end portion of the brake band engages stopmeans in accordance with the direction of rotation of the braked drum tothereby provide a slack end portion of the brake band, while the otherend portion of the brake band provides a tight portion to which isimparted a spring force having a predetermined characteristic.

2 Claims, 10 Drawing Figures P'A'TENTEU MAR28 1972 SHEET 1 BF 4 PR/ORART 2 PR/ORART FR/CT/ON COEFF/C/ENT mwmsk mikqmm IN VENTOR BY yow w hATTORNEYS PATENTEDmza m2 3, 651,899

sum u 0F 4 3.1 E /OM10; 4,2

BRAKE DEVICE IN TAPE RECORDER This invention relates to a brake deviceused with the reel bed or the like in a tape recorder.

Generally, in the reel bed or the like of a tape recorder, a differentbraking force (or different directivity of the braking force) isrequired in accordance with the direction of rotation of the reel bed.Usually, the suitable directivity ratio for the braking force is 2 l inaccordance counter-clockwise the variation in the amount of the tapewound on the reels, and it is required that a pair 'of such reel beds bearranged symmetrically to each other so as to ensure the smooth rotationthereof without causing the tape to be slack or broken in use. Accordingto the prior art the braking operation has usually been mostlyaccomplished by the press contact of a friction shoe with the brakeddrum of the reel bed.

For example of the prior art brake device is shown in FIG. 1. In thisdevice, a brake band 15 has one end thereof connected to a spring 17through a lever 16 and the other end connected to a pivotally mountedshaft 18. The braking torque provided by a such brake device for thecounterclockwise rotation of the reel bed 1 is expressed by thefollowing equation:

Hence, the directivity ratio between the two braking torque is thus:

MBN/MBRZBLH T represents the tension in the tight end portion of thebrake band during the counter-clockwise rotation of the reel bed, T thetension in the slack end portion of the brake band during the clockwiserotation of the reel bed, T the tension, in the slack end portion of thebrake band during the clockwise rotation of the reel bed, the angle ofcontact of the brake band with the braked drum (FIG. 2 relates to thecase where 0 180), p. the coefficient of friction between the brakeddrum and the brake band, R the radius of the braked drum, M the brakingtorque during the counter-clockwise rotation of the reel bed, and M thebraking torque during the clockwise rotation of the reel bed.

The foregoing equations (2) and (4) correspond to curves a and b of FIG.2, respectively, which indicates that the value of M or braking forceduring the counter-clockwise rotation of the reel bed is greatly variedwith the variation in the friction coefficient ;1.. It is also apparentfrom the equation (5) that the directivity ratio is increased in termsof exponent. For example, if n is coefficient, the initial frictioncoefficeint, B the braking force during the counter-clockwise rotationof the reel bed and A the braking force during the clockwise rotation,as shown in FIG. 2, then the directivity ratio is approximately 2 1,whereas if the friction coefficient is varied to a, 0.5, the brakingforces during the respective rotations will be 13 and A and accordinglythe directivity ratio between these braking forces will be sharplyincreased from 2 l to 4.5 I.

With the prior art brake device, the friction coefficient thus tends toincrease with the use of the device. Especially with the band type brakedevice, the braking force provided thereby varies approximately inproportion to a value having the friction coefficient as the exponentthereof and such variation affects the directivity ratio so greatly thatthe latter increases even up to a ratio two or three times as high as aninitially set value. More specifically, if the initially set directivityratio is 2 1, the ratio will be increased to 4 1 l to 6 l, and

such a great increase in the directivity ratio results in breakage,dilation or other damage of the tape during use.

It is an object of the present invention to provide a brake device whichcomprises a brake band entrained on a braked drum, spring meansconnected to the ends of said brake band,

and stop means separately provided adjacent to said ends of said brakeband, whereby one end portion of said brake band engages one of saidstop means in accordance with the direction of rotation of said brakeddrum so as to provide a slack portion of said brake band which is freefrom any spring force while the other end portion of said brake bandprovides a tight portion to which is imparted a spring force having apredetermined characteristic.

It is another object of the present invention to provide a brake devicewhich comprises a brake band entrained on a braked drum, said brake bandhaving their ends connected to a lever at two points therein, andresilient means interconnecting said lever and a fixed portion in such amanner that the end of said resilient means connected to said lever liesat apoint which divides the distance between said two points of saidlever, said resilient means being designed so as to exert a component offorce on the tight portion of said brake band during the rotation ofsaid braked drum in either direction.

According to the present invention, the brake band entrained on thebraked drum is movable in the direction of rotation of the braked drum,whereby one end portion of the brake band engages stop means to providea slack portion of the brake band in accordance with the direction ofrotation of the braked drum while the otherend portion of the brake bandprovides a tight portion to which is imparted a spring force having apredetermined characteristic. Thus, as the friction coefficientincreases during the operation of the brake band, the tension in theslack portion of the brake band approaches zero so that the brakingforce is determined only by the spring force exerted on the tightportion of the brake band substantially without being affected by thevariation in the friction coefficient. This leads to the provision of ahighly stable and novel brake device.

With the prior art brake device, it has been impossible to predetermineor foresee the limit of the variation in friction coefficient. Incontrast, according to the present invention, the friction coefficientcan always be limited within a predetermined allowable value so that anyinconvenience resulting from too great a variation in the frictioncoefficient may be completely prevented. Also, such an allowable limitand the directivity ratio are determined only be the selection of theresilient forces for two springs, and this leads to the elimination ofthe need to pay minute attention to the materials forming the brake bandand braked drum, the workmanship of such members, the value ofcoefficient of friction therebetween and other factors. Moreover, anyvariation in the friction coefficient during the use of the brake devicemay be substantially negligible. Thus, the brake device according to thepresent invention is very excellent in working life and stability ofperformance as well as simple and easy to manufacture, and thus iteliminates the drawbacks peculiar to the prior art brake device.

The invention will now be described by way of example in conjunctionwith the accompanying drawings, in which:

FIG. 1 is a schematic front view showing an example of the brake deviceaccording to the prior art;

FIG. 2 is a graph for illustrating the relation between the frictioncoefficient and braking forces provided by the device of FIG. 1;

FIG. 3 is a schematic front view showing an example of the brake deviceaccording to the present invention;

FIGS. 4 and 5 are similar front views but showing the device of FIG. 3in different operative positions;

FIG. 6 is a graph for illustrating the relation between the frictioncoefficient and braking forces provided by the device of FIG. 3;

FIGS. 7 to 9 are schematic front views showing another example of thebrake device according to the present invention, and illustrating thedevice in variousoperative positions; and

FIG. 10 is a schematic front view showing the brake device of FIGS. 7 to9 as applied to the reel device in a tape recorder.

Referring to FIG. 3 which shows an example of the brake device accordingto the present invention, there is seen a reel bed 101 and a brake band102 entrained on a braked drum provided by the reel bed 101. One end 103of the brake band 102 is secured to an arm 107 at one end thereof. Thearm 107 has a spring 105 connected thereto and is pivotally mounted bymeans of a shaft 106. The arm 107 is normally urged by the spring 105 soas to engage stop means 108. The other end 104 of the brake band 102 isconnected to a spring 109 by means of a lever 110 mounted for pivotalmovement about a shaft 112. The resilient force of the spring 109 isselected to be at a lower level than that of the spring 105 so that thebrake band 102 is normally urged by the spring 105 so as to maintain thelever 110 slightly disengaged with stop means 111. The slightdisengagement between the lever 110 and stop means 111 allows the brakeband 102 to move in the direction in which the braked drum is rotated.This arrangement is such that either the arm 107 or the lever 110 isautomatically and selectively engaged with the stop means 108 or 111 inaccordance with the direction of rotation of the braked drum. Anelectromagnet 113 is provided to release the brake during the operation,and this electromagnet is provided with a plunger having a pin 1 14studded at the lower end thereof.

Description will now be made of the operation of the abovedescribedbrake device.

FIG. 3 shows the brake device in a braking position. If the brakereleasing electromagnet 113 is energized with the brake device in thisposition, the plunger is raised by the electromagnet so that the pin 114studded in the plunger engages the lever 110 to rotate the levercounter-clockwise and thereby release the brake as shown in FIG. 4. Whenthe reel bed 101 is rotating counter-clockwise, a braking force in thecounterclockwise direction as indicated by an arrow b is imparted torotate the brake band 102 together with the braked drum in the directionb so as to engage the lever 110 with the stop means 111. Thus, thespring 109 has its resilient force nullified while the other spring 105alone is at work, whereby there is established the relation as expressedby the aforementioned equation (4), which vmeans the same characteristicas that shown by a curve a" in FIG. 6. If a braking force is imparted tothe reel bed 101 when it is rotating in the clockwise direction asindicated by an arrow a in FIG. 3, the arm 107 then engages the stopmeans 108 to nullify the resilient force of the spring 105 and leave thespring 109 alone at work. Thus, there is established the relation of theequation (4) as in the abovedescribed case of the counter-clockwiserotation, to thereby provide the same characteristic as that shown bythe curve a.

Accordingly, in the same way as in the case of the equation (4),.thebraking torque for the counter-clockwise rotation of the reel bed 101(i.e. the case of FIG. 5) will be expressed as:

Similarly, the braking torque for the clockwise rotation ITe. the caseof FIG. 3) will be expressed as:

:I-Ience, the brake device of the present invention has the directivityratio expressed as follows:

0* 1 7 MBN 1 M BR 0 1) E TgR This means that the directivity ratio of the "Brake deviceis determined only by the tensions T and T of the springs105 and 109, thus resulting in the characteristic curves b" and a" asshown in FIG. 6, which relates to the case where 0 equals 180.

Referring to FIG. 7, there is shown another embodiment of the presentinvention. This alternative example includes a braked drum 201 rotatablymounted on a shaft 202. A brake band 203 is entrained peripherally ofthe braked drum 201 and has the ends thereof secured to a lever 204 at205 and 206. Resilient means 207 is provided between the lever 204 and afixed portion 209 to interconnect them. One end of the resilient means207 is secured to the lever 204 at a point 208 which divides thedistance between thepoints 205 and 206 into a desired ratio a b and theother end of the resilient means a la secured to a b portion 209. Stoppins 210 and 21 1 are provided to restrict the movement of the lever204.

In the normal position of the FIG. 7 device, if the force of theresilient means 207 is represented by T components of force T and Texerted on the respective points 205 and 206 in the lever 204 will be:

If a braking force is imparted to the braked drum 201 when it isrotating in the clockwise direction A as shown in FIG. 8, then thecomponent of force T will be:

T, T e. 9

where T represents the tension produced in the slack end portion of thebrake band 203 during the rotation of the braked drum 201 in thedirection A, e the base of natural logarithm, p. the coefficient offriction between the braked drum 201 and the brake band 203, and 0 theangle of contact of the brake band 203 with the braked drum 201. As aresult, there is provided the following braking torque M If, on theother hand, the braked drum 201 is rotated in the counter-clockwisedirection B, the lever 204 will be slightly rotated for disengagementfrom the stop pin 210 and for engagement with the other stop pin 211. Inthis position the braking torque M will be expressed as:

T represents the tension produced in the slack portion of the brake band203 during the rotation of the braked drum 201 in the direction B.

The characteristics of the braking forces thus derived by the equations(13) and (16 are shown in FIG. 6, which indicates that the brakingforces increase with the increase of the friction coefficient p. butthey converge for the predetermined values of LR and ER. Therefore, asshown by the curves in FIG. 6, there is provided a much less variable,stable braking characteristic. The directivity ratio between the brakingforces can be derived from the previous equations (13) and 16) asfollows:

a MB -l- TOR a FIG. shows the braking device of the present invention asapplied to the reel mechanism of a tape recorder. Numeral 212 denotes aplunger type electromagnet having a braking rod movable integrallytherewith. Movement of the braking rod 213 controls the release of thebrake band 203.

As has been described above, the brake device of the present inventioncomprises a brake band entrained on a braked drum and having their endsconnected to a lever at two points thereof, and resilient meansinterconnecting the lever and the fixed portion of a tape recorder. Theend of the resilient means connected to the lever is located at a pointwhich divides the distance between the aforesaid two points of the leverinto any desired ratio, so that a component of force is exerted on thebrake band during the rotation of the braked drum in either direction.This arrangement results in the following advantages:

a. For any variation in'the friction coefficient, there is obtained aless variable braking force showing a stable braking characteristic; and

b. The directivity of the braking force is not affected at all by thefriction coefficient, but is always maintained at a predetermined ratio.

Thus, the present invention provides an ideal brake device which is freefrom any trouble such as breakage of the tape and which is simple inconstruction as shown in the foregoing embodiments.

What is claimed is:

l. A brake device, comprising:

a brake band fitted to the contour of a braked drum:

an arm having one end connected with one end of said brake band, saidarm being pivotally supported at the other end thereof;

a lever having one end connected with said other end of said brake band,said lever being pivotally supported at the center thereof;

a first spring means having one end connected to said one end of saidarm and having the other end fixed stationary;

a second spring means having one end connected to said one end of saidlever and having the other end fixed to a stationary member;

wherein said first and second spring means are arranged such that whenthe brake device is shifted into a braking position said brake band ispressed against the braked drum due to the tension of both said springmeans;

a first stop means fixed near said arm and said first spring means, saidfirst stop means being spaced at a predetermined distance from said arm;and

a second stop means fixed near said lever and said second spring, saidsecond stop means being spaced at a predetermined distance from saidlever, whereby one end portion of said brake band is hindered fromfurther movement when at least one of said arm and said lever engagesone of said corresponding stop means in accordance with the direction ofrotation of said braked drum to provide a slack portion of said brake atsaid one end which is free from any spring force while the other endportion of said brake band provides a tight portion to which is imparteda predetermined spring force.

2. A brake device, comprising:

a brake band fitted to the contour of a braked drum;

a lever having its ends connected to ends of said brake band,

respectively;

resilient means interconnecting said lever and a fixed point of saidbrake device such that the end of said resilient means connected to saidlever lies at a point which divides the distance between said ends ofsaid lever and such than when said brake device is shifted into abraking position said brake band is pressed against said braked drum dueto the tension of said resilient means; and

first and second stop means respectively fixed to stationary means nearsaid ends of said lever and spaced at predetermined distances from saidends,

whereby said resilient means exert a component of force on the tightportion of said brake band during the rotation of said braked drum ineigher dirsctign.

1. A brake device, comprising: a brake band fitted to the contour of abraked drum: an arm having one end connected with one end of said brakeband, said arm being pivotally supported at the other end thereof; alever having one end connected with said other end of said brake band,said lever being pivotally supported at the center thereof; a firstspring means having one end connected to said one end of said arm andhaving the other end fixed stationary; a second spring means having oneend connected to said one end of said lever and having the other endfixed to a stationary member; wherein said first and second spring meansare arranged such that when the brake device is shifted into a brakingposition said brake band is pressed against the braked drum due to thetension of both said spring means; a first stop means fixed near saidarm and said first spring means, said first stop means being spaced at apredetermined distance from said arm; and a second stop means fixed nearsaid lever and said second spring, said second stop means being spacedat a predetermined distance from said lever, whereby one end portion ofsaid brake band is hindered from further movement when at least one ofsaid arm and said lever engages one of said corresponding stop means inaccordance with the direction of rotation of said braked drum to providea slack portion of said brake at said one end which iS free from anyspring force while the other end portion of said brake band provides atight portion to which is imparted a predetermined spring force.
 2. Abrake device, comprising: a brake band fitted to the contour of a brakeddrum; a lever having its ends connected to ends of said brake band,respectively; resilient means interconnecting said lever and a fixedpoint of said brake device such that the end of said resilient meansconnected to said lever lies at a point which divides the distancebetween said ends of said lever and such than when said brake device isshifted into a braking position said brake band is pressed against saidbraked drum due to the tension of said resilient means; and first andsecond stop means respectively fixed to stationary means near said endsof said lever and spaced at predetermined distances from said ends,whereby said resilient means exert a component of force on the tightportion of said brake band during the rotation of said braked drum ineither direction.